This is Miles of Music Island Camp.

The 12-minute motorboat ride from Meredith, New Hampshire, across Lake Winnipesaukee transports them to another world. Cellphones disappear into cabin drawers while the sounds of fiddles, banjos, and guitars drift through the pine trees of Three Mile Island. Since 2011, novices and professionals alike have made the pilgrimage to Miles of Music Island Camp. Some come for their first time, others for their 14th.

For most of the summer, the Appalachian Mountain Club, a nonprofit that bills itself as the nation’s oldest conservation and recreation group, operates a rustic camp on this 43-acre, private, wooded isle in the northwestern corner of Winnipesaukee. But for one week in June, nature-seekers are replaced by musicians, gathering to explore the marriage of folk music and modern songwriting.

“It’s creativity camp for grown-ups,” says cofounder and director Kristin Andreassen.

Days begin with coffee at the camp store before pancakes in the dining hall. Then there are classes in songwriting, Cajun fiddle playing, and much more — all taught by ear. Afternoons find people sprawled on the dock, with some braving the high jump into the cold lake water. Others disappear into instrument-specific lessons. Family-style dinners lead to nightly events: one night it’s karaoke backed by a full band, another it’s a talent show, and on another campers gather around a bonfire, singing into the early hours.

Threading through it all is Dinty Child. At nearly 70, he’s the first up each morning for yoga, jumps in the lake daily regardless of weather, leaps off his guitar amp at karaoke’s close, and leads a musical midnight boat trip under the moon. As a full-time employee of the Appalachian Mountain Club, Child manages the island in the offseason. As a founding member of the Boston roots collective Session Americana, he is “the link between the island and the music,” Andreassen says.

“There would be no Miles of Music without Dinty,” she says. Their friendship began in the Boston music scene of the early 2000s, when Andreassen, who now lives in Nashville, regularly performed with Child and Laura Cortese, the other cofounder of the camp, in a collective called Sub Rosa. In 2010, Dinty brought Sub Rosa to the island for a retreat and Andreassen instantly pictured a camp taking shape. “The location invited it,” she says. Looking at the rec hall, with its glass doors opening out onto the lake, “I could just envision a square dance happening there.”

A year later, the camp launched, with touring professionals sleeping in the same rustic, no-electricity cabins as total beginners.

“It’s about helping all the things that go too quickly in life to slow down,” Andreassen says, “so that we can move more quickly in the things that matter most, like friendships and art.”